The breath hydrogen test was used to determine the prevalence of lactorse malabsorbers after drinking of a cup of milk (250-ml), in healthy Thai adults, 20-45 years old. Based on the highest hydrogen production of (...) 20 ppm, of thirty two, twenty eight subjects (88%) had hydrogen levels suggestive of lactose malabsorbers

of these, twenty-four of these sujects (75%) had uncomfortable gastrointestinal symptoms after ingestion of a cup (250-ml) of cows milk. Half a cup of milk (125-ml) and a cup (250-ml) of cows milk with solid foods were given separately to lactose malabsorbers. Based an hydrogen production ten out of twenty-four lactose malabsorbers (42%) could digest lactase in 125-ml cows milk and five out of twenty-three of them (22%) digested digest lactose in 250-ml cows milk when consumed with with solid foods. The mean peak-rise of breath ghdrogen in all lactose malabsorbers with 125-ml cows milk was 26(+)(,-)3 ppm (mean(+)(,-)SEM) and with 250-ml cows milk plus solid foods was 36(+)(,-)4 ppm (mean(+)(,-)SEM) which were significantly lower (P<0.05) than with 250-ml cows milk (58(+)(,-)7 ppm) alone. The prsented time of the highest peak-rise in breath hydrogen was displaced from the 4.5 postprandial hour with 250-ml cows milk alone to the 5.6 postprandrial hour with 250-ml cows milk plus solid foods. In addition, the intensity of gastrointestinal symptoms in lactose malabsorbers with 125-ml cows milk and with 250-ml cows milk plus solid foods were significantly lower (P<0.05) than with 250-ml cows milk. Thus, the madification of postprandial lactose fermentation in Thai people by reduction of milk volume from a cup to half a cup 250-ml to 125-ml and by drinking milk with solid foods can substancially reduce the postprandial colonic fermentation which in turn reduce the intensity of lactose malabsorption as well as gastrointestinal symptoms.